Passive microwave measurements of snow-covered forest areas in EMAC'95

Airborne passive-microwave signatures collected in Northern Finland during EMAC-95 are analyzed with the emphasis on forested areas and dry snow condi tions, The microwave signatures cover the 6.8-18.7-GHz frequency range and were acquired at both vertical and horizontal polarizations. The analysis i s carried out with respect to the forest-stem volume data and comprises thr ee different snow-depth situations. Emissivities approach saturation limit with the increasing stem volume. At 10.65 GHz, the saturation level was fou nd to be linearly related to the snow-water equivalent, On the basis of pas sive-microwave measurements, an empirical forest transmissivity model is de veloped, The model is valid at vertical polarization 50 degrees incidence a ngle, and it accounts for microwave frequency and forest-stem volume effect s in the range of 6.8-94 GHz and 0-150 m(3)/ha, respectively.